Generator Circuit Breaker Based on Pre-Charged Capacitor Commutation and Thyristor Freewheeling

Generator circuit breaker (GCB) can realize reliable isolation between generator and system under different conditions to avoid damage of equipment. With the increase of alternator capacity, GCB with higher rated current and short-circuit breaking capacity is required. In scenarios with large rated currents, vacuum switches are difficult to apply due to insufficient heat dissipation capacity, while gas switches are prone to re-breakdown under high transient recover voltage (TRV). Moreover, the severe ablation when short-circuit current is large will result in a short electrical life of the switch. Aiming at the technical difficulties of current GCB equipment, this paper proposes a GCB based on pre-charged capacitor commutation and thyristor freewheeling, which provides zero-voltage dielectric recovery time for gas mechanical switches by paralleling freewheeling thyristors. The proposed GCB has the advantage of low cost, long life and can break short-circuit current with high DC components. In this paper, the topology, principle and parameter characteristics of the proposed GCB are studied, and the parameter design method is proposed accordingly. The breaking test of the scaled equivalent prototype is carried out, which verified the feasibility of the principle of proposed GCB and the effect of the freewheeling thyristor.